TOPOLOGICAL, SIZE AND SHAPE OPTIMIZATION OF AN UNDERWING PYLON SPIGOT

Transcription

1 TOPOLOGICAL, SIZE AND SHAPE OPTIMIZATION OF AN UNDERWING PYLON SPIGOT Prepared by: M. Basaglia (Alenia Aermacchi), S. Boni Cerri (Alenia Aermacchi), G. Turinetti (Altair)

2 Topological, Size and Shape Optimization of an Underwing Pylon Spigot Aircraft pylons have the function of supporting external payloads and are installed under the wing and / or the fuselage. Pylons that are being developed in Alenia Aermacchi will be installed on M-346 new advanced training aircraft. Inside the pylon, the structure called spigot or, in some cases, pivot is a highly stressed structure made of high resistant steel and is the component that transfers the concentrated loads coming from the carried mass to the wing or fuselage structure. The design activity started from the available space envelope, from the interfaces that were defined as non-design zones and the sizing loads (a set of 26 load cases). The application has been performed using OptiStruct. Two subsequent optimizations have been conducted: the first one followed a topological approach, the second one was set as a shape optimization. 2

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4 Applied force - upper node RBE3 area for the WING/SPIGOT interface force application. RBE3 area for the WING/SPIGOT interface force application. Applied force - lower node CELAS - X, Y, Z direction Spigot constrained to the ground (conservative approach) through celas elements 4

5 Stress - max principal 5

6 Present spigot configuration Weight = kg 6

7 Starting volume 26 load cases Non design area Non design area 7

8 Main advantage of topological optimization is to easily check how the structure is designed by the optimization tool in relation to some different design and manufacturing strategies (objective, responses and constraints). First optimization iterations are developed with the objective of minimum weight compliance referred to all load conditions (with the same weight equal to 1). Constraints: mass fraction, minimum dimension, stress level, planes of symmetry, direction of machining. 8

9 Responses: Weight compliance, mass fraction Constraint: mass fraction 0.25 Objective: MIN weight compliance 9

10 Responses: Weight compliance, mass fraction Constraint: mass fraction 0.25 Manufacturing constraints: XZ plane of symmetry, mindim in the whole design space Objective: MIN weight compliance 10

11 Responses: Weight compliance, mass fraction Constraint: mass fraction 0.25 Manufacturing constraints: YZ and XZ planes of symmetry, mindim in the whole design space Objective: MIN weight compliance 11

12 Responses: Weight compliance, mass fraction, stress Constraint: mass fraction 0.25, maximum principal stress<1000mpa in the non design area Manufacturing constraints: XZ plane of symmetry, mindim in the whole design space 1 draw direction (Z) Objective: MIN weight compliance 12

13 Responses: Weight compliance, mass fraction, stress Constraint: mass fraction 0.25, maximum principal stress<1000mpa in the non design area Manufacturing constraints: XZ plane of symmetry, mindim in the whole design space, 2 design spaces in order to define draw directions (X, Z) Objective: Min weight compliance 13

14 Responses: Weight compliance, mass fraction, maximum stress Constraint: mass fraction 0.25 Constraint: stress in the critical area (highlighted in the above figure) 1000 MPa Manufacturing constraints: XZ plane of symmetry, mindim in the whole design space, 1 draw direction (Z) Objective: MIN weight compliance 14

15 Response: Mass, displacement Constraint: Displacement constraint on the top of the Spigot extracted from the starting configuration. Manufacturing constraints: XZ plane of symmetry, mindim in the whole design space, 1 draw direction (Z) Objective: MIN mass 15

16 Shape optimization phase Side flange thickness Spigot base radius (dense Mesh) Side cutout size Lower hole diameter Spigot conicity Lower transverse stiffener thickness 16

17 Optimization problem definition: Objective = Minimize Mass Constraints = Stress Sigma max Bolt forces F max In the above figure, the highlighted areas represent a dense mesh zone, where the stress response is checked. The mass growth is due to the approximation coming from the topological optimization and the redesigning of new CAD with some violation of stress constraint. 17

18 Spigot final configuration The above figure shows the contours of shape changes, where the red area represents the biggest parameter reduction. 18

19 Configuration and mass evolution Present weight FEM weight = kg CAD weight = Kg Weight at the beginning of the shape optimization FEM weight = kg CAD weight = Kg Weight at the end of the shape optimization FEM weight = kg CAD extimated weight = Kg The weight reduction between the starting configuration and the configuration at the last optimization is of 5% 19

20 Conclusions The topological optimization phase gave the evidence of the possibility of saving weight removing material in some areas, compared to the traditional design, in a way that with a standard sizing approach is difficult to imagine. The shape optimization permitted to refine the previously identified design. An interesting weight reduction (for this kind of structure) of 5% has been obtained. 20

21 Q & A Thank you for your attention 21